The primary objective is to test for age differences in decay rates in short-term memory. This will be accomplished by developing a measure of decay rate, using signal detection as a distractor task in the Brown-Peterson task in conjunction with Reitman's (1) seven-measures analysis. On the basis of stimulus persistence theory (2), which posits longer duration of neural encodings of stimuli in the nervous systems of old adults than young adults, as well as on the basis of several other lines of reasoning, it is predicted that elderly adults will display slower rates of decay of information from short-term memory than young adults. One secondary objective will be to measure memory spans and scanning (3) rates, and then to use decay rates and scanning rates in a test of a decay model (4) of memory span performance and to explain the relative lack of age differences in memory span. The decay model will also be tested by considering differences in decay rates as a function of material type (digits and words). A similar, but exploratory, analysis will attempt to explain the relative lack of age differences in the recency effect in free recall by means of scanning rates and decay rates. Ancillary analyses will also include assessment of the value of individual differences in decay rates, scanning rates, memory spans, and recency effects in predicting various intellectual abilities as revealed by scores on selected WAIS subscales. The development of the decay rate measure is expected to contribute to the experimental psychological analysis of the decline in memory proficiency with normal aging as well as the more serious declines observed in Alzheimer's disease. The decay rate measure should ultimately be able to serve as a diagnostic tool in predicting individual differences in intellectual performance (such as arithmetic reasoning) and in predicting or diagnosing Alzheimer's disease.